Electrical systems operate by providing different potential levels, (e.g., voltage levels) to various points in the system. These differences in potential levels can cause current to flow through loads disposed between the different potential levels. This current may be used to drive various types of electrical devices.
Many electrical systems include at least one zero potential level referred to as a ground level. In certain systems a single point ground may be provided, which serves as a zero volt potential level for the system. That is, any or all other potential levels in the system may be referenced with respect to the single point ground.
Other systems, however, may include multiple ground points. In many applications, it may be desirable to maintain these multiple ground points at the same potential level (e.g., zero volts). Maintaining each of the multiple ground points at a common potential level may help to ensure consistency within the electrical system. For example, maintaining the ground points at a common voltage level could ensure that measurements of various signals associated with the electrical system would be consistent regardless of which ground point was used as a reference point. Further, maintaining the ground points at a common voltage level could help to minimize or prevent undesirable leakage current between the ground points.
Maintaining multiple ground points at a common voltage level can be challenging. Simply connecting the multiple ground points to each other using wire connectors may not provide the desired effect. For example, wires include a certain resistance that depends on factors such as wire thickness, length, and material. For short lengths of wire, the resistance may be negligible. For longer lengths of wire, however, the resistance may be significant. This resistance may cause two ground points connected by the wire to reside at different potential levels when a current is allowed to flow in the wire. The magnitude of the potential difference between the two ground points may depend on the total resistance of the wire and the magnitude of the current flowing in the wire. As the magnitude of the current in the wire increases, the potential difference between the two ground points also will increase.
Electrical systems have been proposed that monitor differences between two potential levels and compensate for these differences. For example, U.S. Pat. No. 5,869,909 (“the '909 patent”) describes an active ground compensation system that senses a voltage difference between a neutral reference node and a ground node of a power line communication system. In response to a difference between these nodes, the ground compensation system drives the ground node to reduce the voltage difference between the voltage of the ground node and the voltage of the neutral reference node.
While the ground compensating electronics of the '909 patent may compensate for potential differences between two nodes in an electrical system, the configuration disclosed may be problematic and not suitable for many types of applications. For example, complicated electronics may be required for actively driving the ground node to a potential level equivalent to that of another node. Further, the ground compensating circuitry of the '909 patent is directed toward solving problems associated with electrical power systems for homes and may have limited use in other types of electrical systems.
The present invention is directed to overcoming one or more of the problems or disadvantages existing in the ground compensation methods and apparatus of the prior art.